After reading my September column about using the heart as a guide for energy efficient HVAC design, a forward-thinking ES reader asked about using the respiratory system to think about air handling strategies. We could clearly use some help with this topic as the debate rages on about the key metric of indoor air management. Do we prioritize low-energy consumption with a bow to “human comfort” or do we prioritize human health (not merely comfort) and hope that we do not raise building fuel consumption in the process? Let’s ask Mother Nature about how she manages gas exchange in the most energy-efficient way.
In mammals (this includes humans), life–supporting gas exchange occurs in the innermost part of our lungs, in tiny air sacs called the alveoli. The ultimate job of each alveolus is to allow inhaled oxygen to get into our blood stream, and simultaneously remove excess carbon dioxide, the waste product of our metabolism. This gas exchange occurs through passive diffusion, so the air and blood sides of the alveoli can only be separated by one thin membrane.